1. Field of the Invention
The present invention relates to a method for decoding an address in pre-groove (ADIP) data of an optical disc drive, and more specifically, to a method for decoding ADIP data by comparing ADIP data with signals generated by quotient summation.
2. Description of the Prior Art
Please refer to FIG. 1 showing a conventional optical drive reading a track 12 of an optical disc 10. In the DVD+R/RW disc 10, the track 12 can be divided into two types: a data track 14 for recording data and a wobble track 16 for recording ADIP data corresponding to sections on the disc. The data track 14 spirals around the center of the disc 10 following the track 12, and the wobble tracks 16 also spiral around the center of the disc 10, however, they wobble up and down in a small amplitude. In addition, the wobble tracks 16 are continuous protruding tracks, and the data track 14 is located in the groove formed between two wobble tracks 16. The data track 14 has continuous record signals 18 (corresponding to pits) of different lengths and different characteristics of reflection. These record signals 18 represent different data information, thus the disc 10 can record data by controlling the length of the record signal 18.
A pickup head 20 of an optical disc drive includes four sensors Sa, Sb, Sc, Sd for reading data in the wobble tracks 16. Since the characteristics of reflection of the groove and the protruding tracks differ from each other, the reflection sensed by the sensors Sa, Sb, Sc, Sd differs accordingly, thus wobble signals can be obtained by calculating sensed values of the sensors Sa, Sb, Sc, Sd. As the disc 10 rotates, the pickup head 20 follows the disc 10 along the direction shown by arrow 22 to read the sensed values along the track 12. For instance, when the pickup head 20 is located at P1, the position of the sensors Sa, Sd corresponds to the groove of the data track 14, and the position of the sensors Sb, Sc corresponds to the protrusion of the wobble track 16. When the pickup head 20 is located at P2, the sensors Sa, Sd, originally located over the groove, move to the position over the protrusion of the wobble track 16. Additionally, the sensors Sb, Sc, originally located over the protrusion of the wobble track 16, move to the position over the groove of the data track 14. Accordingly, the sensed value as well as the wobble signal change. In such a manner, the pickup head 20 generates the wobble signals according to the wobble track, and the wobble signals can be decoded into address in pre-groove (ADIP) data.
Please refer to FIG. 2 to FIG. 4 respectively showing conventional wobble signals 24, 26, 28. Every two record sections on the disc 10 correspond to 93 wobble periods, wherein 8 wobble periods record the ADIP data using phase modulation (PM). As shown in FIG. 2, the wobble signal 24 includes 8 wobble periods W0, W1, W2, W3, W4, W5, W6, W7 recording the ADIP data using phase modulation. In the wobble periods W0, W4, the phase of the wobble signal 24 changes by 180 degrees, and in this case, the wobble signal 24 corresponds to an ADIP sync unit. As shown in FIG. 3, the wobble signal 26 includes 8 wobble periods W0, W1, W2, W3, W4, W5, W6, W7 recording the ADIP data using phase modulation. In the wobble periods W0, W1, W6, the phase of the wobble signal 26 changes by 180 degrees, and in this case, the wobble signal 26 corresponds to an ADIP data unit being “0”. As shown in FIG. 4, the wobble signal 28 includes 8 wobble periods W0, W1, W2, W3, W4, W5, W6, W7 recording the ADIP data using phase modulation. In the wobble periods W0, W1, W4, W6, the phase of the wobble signal 28 changes by 180 degrees, and in this case, the wobble signal 28 corresponds to an ADIP data unit being “1”.
As described above, the decoding of ADIP data plays an important role when burning the DVD+R/RW disc. The ADIP data includes all the information on the DVD+R/RW disc, and the frequency of the wobble signal represents the linear speed of disc rotation. For constant linear velocity (CLV) reading, the wobble signals are utilized as feedback signals to a spindle motor. And for constant angular velocity (CAV), the wobble signals are used to generate writing clocks. However, the wobble signals may be interfered with due to defects on the disc, noise, or laser power fluctuations, so that the ADIP data may be lost or the frequency of the wobble signals may be unstable.